<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">

    <title></title>
    <link rel="stylesheet" type="text/css" href="../../../css/layout_flex.css">
    <style>
        /*#parent {*/
            /*display: flex;*/
            /*align-items: center;*/
            /*background: #5fff13;*/
            /*height: 300px;*/
        /*}*/

        /*或*/
        #parent {
            display: flex;
            background: #5fff13;
            height: 300px;
            flex-direction: column;
        }

        .son1 {
            align-self: flex-start;
        }
        .son2 {
            align-self: center;
        }

        .son3 {
            align-self: flex-end;
        }

        /*或*/
            /*原理：这个尚未搞清楚，应该是flex使margin上下边界无限延伸至剩余空间并平分了*/
        /*#parent {*/
            /*display: flex;*/
        /*}*/

        /*#son {*/
            /*margin: auto 0;*/
        /*}*/


    </style>
</head>
<body>

<div id="parent">
    <div class="son1"> 儿子1</div>
    <div class="son2"> 儿子2</div>
    <div class="son3"> 儿子3</div>
</div>
</body>
</html>